1. Technical Field
Exemplary embodiments of the present disclosure relate to a method and apparatus for beamforming in a wireless device.
2. Description of the Related Art
To meet the demand for wireless data traffic having increased since deployment of 4G communication systems, efforts have been made to develop an improved 5G or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘Beyond 4G Network’ or a ‘Post LTE System’.
The 5G communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems.
In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud Radio Access Networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), reception-end interference cancellation and the like.
In the 5G system, Hybrid FSK and QAM Modulation (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed.
In general, connection between wireless devices starts with searching a neighboring wireless device. The wireless device selects a certain communication channel during a search period, stays in a corresponding channel during a certain time, and then moves to another channel. The wireless device may operate in either one of a search mode and a listen mode while staying in each channel. The wireless device transmits a beacon frame to inform neighboring wireless devices of its existence while operating in the search mode. In addition, the wireless device may receive signals from neighboring wireless devices while operating in the listen mode. For example, if the time during which a first wireless device located in a first channel operates in the search mode and the time during which a second wireless device located in the first channel operates in the listen mode are the same, the first wireless device and the second wireless device may search each other's existence.
When the first wireless device which is in the process of beamforming operates in the search mode, the first wireless device generates beacon signals in different beam directions multiple times. For example, the first wireless device in the search mode may transmit beacon signals while changing beams in all directions in which the first wireless device can transmit, in order to inform wireless devices in all directions, with which the first wireless device can communicate, of its existence. The second wireless device in the listen mode may receive at least one beacon signal from the first wireless device in the search mode, and select a beam direction of a beacon signal having the best signal quality from among the received at least one beacon signal. The second wireless device in the listen mode selects the beam direction that the first wireless device will use, and then carries information on the selected beam direction on a sector sweep signal and forwards the sector sweep signal to the first wireless device. In this case, since the second wireless device does not still determine a beam direction that the second wireless device will use, the second wireless device transmits the sector sweep signal while changing beams in all directions in which the second wireless device can transmit. The first wireless device may receive at least one sector sweep signal from the second wireless device, and may select the beam direction that the first wireless device will use and a beam direction of a sector sweep signal having the best signal quality based on the received sector sweep signal. The first wireless device carries the selected beam direction on a sector sweep signal and forwards the sector sweep signal to the second wireless device. Thereafter, the first wireless device and the second wireless device may exchange each other's information or user data with each other.
In the related-art communication between the wireless devices supporting beamforming, the first wireless device and the second wireless device can search for each other only when the time during which the first wireless device operates in the search mode and the time during which the second wireless device operates in the listen mode overlap each other. Therefore, much time is required for the first wireless device and the second wireless device to search for each other. Furthermore, each of the wireless devices should perform a procedure of transmitting beacon signals and sector sweep signals in all transmission-available beam directions (e.g., at most 128 directions in the 802.11ad standard), and thus there may be a long delay in transmitting and receiving data.